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A comparison has been made between assays of Fc receptor bearing cells among blood leucocytes from normal individuals and from patients with myeloid leukaemia, using human anti-D coated erythrocytes (HEA) and sheep erythrocytes sensitised with a rabbit anti-sheep erythrocyte antibody (SEA). Differences were found between the assays in both groups, demonstrating the heterogeneity of Fc receptors with respect to affinity for marker, and for Fc bearing leucocytes. Monocytoid cells reacted more readily with both markers than myeloid cells. The HEA rosette assay may be useful selective diagnostic aid for Fc+ myeloid leukaemia since the SEA assay detects Fc receptors on mature granulocytes.

We describe an acute myelomonocytic leukaemia (E72) devoid of cell-surface HLA-DR antigens, but capable of inducing cellular responses. Leukaemia E72 induced proliferation of normal lymphocytes in primary mixed lymphocyte culture (MLC), which was only weakly inhibited by anti-DR sera. Depletion of a small percentage (congruent to 4%) of DR+ cells on a cell-sorter failed to abrogate the capacity of E72 to stimulate MLC and cell-mediated cytotoxicity (CMC) responses. We found that normal lymphocytes primed with E72 responded in secondary MLC to lymphocytes and leukaemias, suggesting that the lymphocyte-activating determinant (LAD) on E72 is not leukaemia-specific. In addition, E72 induced CMC responses to both leukaemias and lymphocytes. We suggest that E72 may express a novel HLA or non-HLA LAD.

The expression of HLA class I alpha chains by clones derived from a human X mouse T-cell line containing human chromosomes 6 and 15 was analysed by immunofluorescence. Evidence is presented showing that the expression of HLA class I alpha chains is associated with HLA-beta 2m. This is based on the phenotypic and quantitative fluorescence flow cytometric analysis of a series of cloned hybrids. In contrast, HLA and H-2 class I determinants show no evidence of such correlation. Results of cell-sorting indicate that the loss of HLA class I alpha chain expression is due to phenotypic modulation, in addition to gene segregation.

Twenty-two human leukaemias, comprising acute phase leucocytes from 13 acute myeloid and nine lymphoid leukaemias, were tested for susceptibility to spontaneous cell-mediated cytotoxicity (CMC) by untreated lymphocytes and lymphocytes treated for 18 h with 250 IU lymphoblastoid (Namalva) interferon (IFN-alpha). IFN-amplified killing (IAK) by lymphocytes from 24 normal lymphocyte donors was checked on the K562 erythroleukaemia cell line, for comparison with IAK on fresh leukaemias. Nine leukaemias were tested with lymphocytes from three donors, nine with lymphocytes from six donors, three with lymphocytes from nine donors, and one with lymphocytes from 11 donors. Some degree of susceptibility to IAK was found in five acute myeloid and five lymphoid leukaemias, which was markedly dependent upon the source of the effector lymphocytes and did not correlate with the degree of IAK on K562. The 12 other leukaemias were virtually resistant to IAK. The results emphasize the variability in the capacity of IFN-treated lymphocytes to lyse leukaemias that have not been adapted to tissue culture. The basis of effector recognition of cell line and fresh tumour targets is discussed.

Lymphocyte function associated antigen 1 (LFA-1) is a heterodimeric leucocyte adhesion molecule comprising non-covalently associated 95 kD, CD18 and 180 kD, CD11a subunits. Lymphoblastoid cell-lines (LCL) derived from persons with Down's syndrome (Trisomy 21) exhibit increased expression of LFA-1 compared with normal LCL. Although this is probably due to a gene-dosage related increase in the synthesis of CD18, cell-cycle differences between Trisomy 21 (T21) and normal LCL could also influence LFA-1 expression. We have therefore analysed expression of CD18 on G1 and G2M cells using sequential flow cytometry. T21 and normal LCL were co-stained with the DNA-binding vital dye HO342 (Hoechst 33342), and with a CD18 monoclonal antibody. The LCL were first sorted on the basis of HO342 staining into G1 and G2M populations, and these fractions then analysed for CD18 expression. Irrespective of the stage of the cell-cycle, expression of CD18 was increased on T21 compared with normal LCL. Although more CD18 was detected on both T21 and normal G2M compared with G1 cells, the relative density of CD18 in G2M was less than in G1 because G2M cells were larger.

The authors have used a sensitive alkaline phosphatase-anti-alkaline-phosphatase immunohistochemical method to examine 28 human pulmonary carcinomas for the presence of renin. Immunoreactive renin was found in 23 (82%) cases. Specific staining was always associated with small vessels in the stroma of the tumor or in adjacent areas of inflamed fibrous tissue. Within vessels, renin was localized in the cytoplasm of medial cells. Adenocarcinoma exhibited the most consistent staining (11/12 cases), and this appeared to be independent of the degree of tumor differentiation. Immunoreactive renin was also detected in squamous cell (7/8 cases), undifferentiated large cell (4/4 cases), and small cell undifferentiated carcinoma (1/1 cases), but the number of vessels and intensity of staining were usually less than seen in adenocarcinoma. Staining was not found in the bronchioloalveolar variant of adenocarcinoma (0/3 cases). By means of immunoaffinity chromatography with monoclonal antibodies (MAbs) raised to kidney renin, both active and inactive renin were extracted from homogenates of surgical specimens. The molecular weight of both forms of renin was approximately 59,000 daltons.

The relative susceptibility of 10 human leukaemias comprising acute phase leucocytes from 5 acute myeloid and 5 lymphoid neoplasms, and 2 immunoblastic lymphomas to killing by peripheral blood mononuclear cells (PBMC), before and after target cell treatment with phytohaemagglutinin (PHA), and by interleukin-2 (IL-2) activated peripheral blood lymphocytes (PBL) was investigated in short term 51Cr release assays using effector cells from 10 allogeneic donors. Optimal lectin-dependent cellular cytotoxicity (LDCC) was verified against K562 and L1210 cells and lymphokine-activated killing (LAK) against K562 and Daudi cells. Under these conditions, the majority of the leukaemias tested revealed only a finite sensitivity to any of the cytotoxic mechanisms, which was dependent on the donor origin of the effectors. The leukaemias were more consistently susceptible to LDCC than LAK and removal of adherent cells to enrich for the latter activity in effector populations, was ineffective. Lymphocytes from a patient in long term (greater than 5 yr) remission exhibited LAK against the autologous target E84, a natural killer (NK)-sensitive acute myelomonocytic leukaemia. These cells failed to cross-compete for lysis of K562 by LAK cells, suggesting the existence of different recognition structure(s) on the two targets.

Autologous acute myeloid leukaemia (AML), cells caused the suppression of incorporation of 3H-thymidine (3H-Tdr) by remission lymphocytes stimulated with allogeneic cells. In five patients, autologous AML cells suppressed 3H-Tdr uptake by lymphocytes stimulated with up to three different allogeneic cells. Responses to allogeneic AML cells were more strongly suppressed than responses to pooled allogeneic lymphocytes. Suppression was abolished by ultrasonic disintegration of the autologous AML cells, suggesting that a soluble factor was not involved. Suppression was absent from autologous AML cells exposed to ultraviolet light, or when untreated autologous AML cells were present in ratios of less than 1:1 to lymphocytes, or when added 24 or more hours after stimulation of remission lymphocytes with allogeneic cells. It is suggested that suppression is a property of the differentiative level of AML cells, rather than of their malignant properties, although malignant-transformation may bring AML cells into contact with circulating T cells in vivo. Autologous AML cells seem to interfere with the recognition phase of T cell function.

Two hybrid cell lines expressing human CD4 were prepared by fusing human B-lymphoid cells with the mouse T-lymphoma BW5147. Hybrid TF42 was derived from a human B-lymphoblastoid line and TF53.1 from a human B-ALL. Variants of these hybrids expressing or lacking CD4 were isolated by sorting cells stained with the monoclonal antibody (mAb) OKT4 on a fluorescence-activated cell sorter (FACS). Cytogenetic, isoenzyme and DNA analysis confirmed the presence of human chromosome 12 in the CD4+ hybrids, and revealed that CD4 expression by TF42 was associated with multiple copies of this chromosome. Of seventy mAb recognizing human T-cell antigens screened on the CD4+ and CD4- variants of the two hybrids, only mAb recognizing CD4 and Leu 8 reacted with the CD4+ cells. These hybrids should be useful in the preparation, screening and analysis of anti-CD4 monoclonal antibodies, and in studies of CD4 epitopes recognized by HIV.

The expression of human cell-membrane antigens by hybrid cell lines derived by fusing a human B-ALL and mouse BW 5147 T-lymphoma cells has been studied. Using monoclonal antibodies (mAb), the phenotypes of 19 of the 24 hybrids which grew 11-44 days post-fusion have been analysed by indirect membrane immunofluorescence (IF). These uncloned hybrid cells were assayed early after outgrowth, prior to extensive human chromosome and antigen loss. Nonetheless, cytogenetic analysis showed that all hybrids contained variable numbers of human chromosomes. Phenotypic analysis showed that the hybrids could be grouped as follows: a high frequency expressing CD25 (IL-2 receptor), human T200, HLA class I alpha and beta 2microglobulin, and reacting with the mAb H207 and 12E7; an intermediate frequency expressing CD1 and CD2; and a low frequency expressing CD3, CD4, CD5, CD7, CD8 and CD9. This pattern of antigen expression resembled the frequency of these cells in the human B-ALL parent line. Cell sorting was used to immunoselect hybrids expressing CD1 and CD2, but CD1 expression was unstable during subsequent culture.